According to increasing need of organizations and companies to the exchange of information, and regarding this fact that in today’s digital world information security has an important role in information exchange, so encryption is used in order to meet security needs. This study examines Block encryption algorithm such as: Blowfish algorithm and Cellular Automata. Blowfish encryption algorithm is one of the fastest Block symmetrical key encryption algorithms. In this study it is tried to increase the speed of algorithm using Cellular Automata instead of F function of Blowfish encryption algorithm, decreasing F function calculations and as its consequences decreasing the delay of F function of algorithm. Cellular Automata is used because of its ability to produce random numbers. It should be mentioned that is this study in order to increase the security, several rules are added to Cellular Automata. Moreover, same rules have been used that have higher quality in producing random numbers, comparing to other rules. The improved algorithm has been compared to block encryption algorithms AES, DES and Blowfish, regarding speed. This algorithm was implemented by MATLAB software and Active HDL software then santeze time and used memory are measuring by ISE13.2 software. Simulation results show that for 64bit data the speed of proposed algorithm has improved 6% comparing to standard Blowfish algorithm, also show that the usedmemory of proposed algorithm has decreased 5% comparing to standard Blowfish algorithm.